This renewal application for Research Career Scientist (RCS) award seeks to continue the ongoing research activities by the incumbent that have been focused on the molecular pathogenesis of major urinary tract diseases including bladder cancer and kidney stone. Both diseases are highly prevalent among the Veterans, and inflict considerable emotional and physical suffering and staggering medical expenses. Despite the socioeconomic impact, research into the molecular pathogenesis of these diseases remains extremely limited, thus hampering the development of new diagnostic, therapeutic and preventive strategies. During the last award period, the laboratory of the RCS has made significant inroads in defining the key genetic and epigenetic determinants underlying the initiation and progression of bladder cancer and kidney stone. With respect to bladder cancer, the laboratory of the RCS identified several specific combinatorial genetic drivers that are responsible for the genesis and progression of the two major phenotypic variants of bladder cancer, e.g., low-grade superficial papillary tumors versus high-grade invasive tumors. Using a broad range of technical approaches including cultured cell lines, genetically engineered mice, chemical carcinogenesis, analysis of human specimens and high-throughput profiling, the laboratory found that the activation of receptor tyrosine kinase (RTK)/RAS/PI3K pathway collaborates with the loss of 9p21 tumor suppressors (e.g., CDKN2A and CDKN2B) to induce low-grade superficial papillary bladder cancer, and that the same activated RTK/RAS/PI3K pathway collaborates with the deficiency of RB family proteins or that of the p53 pathway effectors to induce high-grade muscle-invasive bladder cancer. In another series of studies supported by a VA Merit Review award, the laboratory of the RCS demonstrated that pyruvate kinase 2 (PKM2), a key enzyme in anaerobic glycolysis or Warburg effect, is upregulated in most bladder cancers and plays a critical role in bladder cancer cell proliferation, and that genetic ablation of PKM2 markedly reduces bladder cancer growth in vitro and in vivo. Inhibition of PKM2 by RNAi or small molecules also greatly decreases the acquired resistance of bladder cancer cells to cisplatin. These and other data to be detailed in the proposal are highly significant in not only improving our understanding of the molecular bases of bladder cancer pathogenesis, but also offer practical insights into novel strategies for bladder cancer diagnostics and treatment. With respect to kidney stone, the laboratory of the RCS continued to make major progress in unraveling the role and mechanisms of action of Tamm-Horsfall protein (THP or uromodulin), the most abundant urinary protein in humans, in urinary tract defense against kidney stone formation. The deficiency of THP renders animal models more susceptible to intra-renal calcification, via increased urinary supersaturation, that strongly resembles the early stages of idiopathic stone formation in humans. Because THP deficiency is often observed in patients, such data will have major implications on kidney stone pathogenesis and prevention. In the past four and a half years, the RCS obtained a VA Merit Award, a multidisciplinary NIH Program Project (PO1) grant and an NIH RO1 grant; published 49 peer-reviewed papers; spearheaded multiple collaborative projects with VA and non-VA investigators; continued to actively train junior faculty members and postdoctoral fellows; provided important services to local and national VA, university affiliates and research community at large. These accomplishments set the stage for the RCS to continue and expand his contributions to the mission of VA and university affiliates in helping advance research, education, patient care, mentoring, services and interdisciplinary collaborations.